Metallic matrix composites of the prior art frequently sustain damage when they are exposed to temperature variations. This damage may include the loss or reduction of mechanical properties such as tensile and shear strengths and the degradation of the structural integrity of the composite. Such composites characteristically comprise at least two different materials having different coefficients of thermal expansion. Because of the differences in thermal expansion and contraction which occur upon heating and cooling respectively, internal stresses can develop when the composite is subjected to temperature variations which lead to either a loss of the mechanical properties of the composite (e.g., its strength) and/or a deterioration of the composite structure (i.e., the composite simply falls apart). The general problem and an underlying basis for the problem are discussed in more detail hereinbelow.
Two patents which generally deal with the problem of the stress induced in composites of two metals by the differential expansion of the metals when heated are U.S. Pat. Nos. 2,421,891 (Keene et al) and 2,468,206 (Keen et al). In the former patent, the end of the component of the composite having the lesser coefficient of expansion is made to extend beyond the end of the other in order to protect an inside weld fillet. In the latter patent, flanges are provided to confine the expansion of the component having the higher coefficient of expansion and a space is left between the component and the flanges in an attempt to reduce the problems resulting from the differential expansion of the two components upon heating. Other patents of possible interest include U.S. Pat. Nos. 2,891,303 (Stephenson), 2,063,325 (McLeod) and 3,544,706 (Aupoix).